"The Mommy Observation" - When Sheldon visits his Mom in Houston, he is forced to confront a new reality. Meanwhile, Raj's "Murder Mystery" party starts some fights within the gang, on a rebroadcast of THE BIG BANG THEORY, Monday, Sept. 1 (8:00-8:30 PM, ET/PT) on the CBS Television Network. (Originally broadcast 3/13/14.)

Leonard and Sheldon are brilliant physicists - geniuses in the laboratory, but socially challenged everywhere else. Enter beautiful, street-smart neighbor, Penny, who aims to teach them a thing or two about life. Despite their on-again, off-again relationship in the past, Leonard and Penny have finally gotten engaged. Even Sheldon has found a female companion, entering into a "Relationship Agreement" with neurobiologist Amy Farrah Fowler. In their free time, Leonard and Sheldon enjoy fantasy role-playing games with their ever-expanding universe of friends, including fellow scientists Koothrappali, Wolowitz and Wolowitz's adorable microbiologist wife, Bernadette.